Abstract
We describe an electrochemical measurement technique that enables bioelectronic measurements of reporter proteins in living cells as an alternative to traditional optical fluorescence. Using electronically programmable microfluidics, the measurement is in turn used to control the concentration of an inducer input that regulates production of the protein from a genetic promoter. The resulting bioelectronic and microfluidic negative-feedback loop then serves to regulate the concentration of the protein in the cell. We show measurements wherein a user-programmable set-point precisely alters the protein concentration in the cell with feedback-loop parameters affecting the dynamics of the closed-loop response in a predictable fashion. Our work does not require expensive optical fluorescence measurement techniques that are prone to toxicity in chronic settings, sophisticated time-lapse microscopy, or bulky/expensive chemo-stat instrumentation for dynamic measurement and control of biomolecules in cells. Therefore, it may be useful in creating a: cheap, portable, chronic, dynamic, and precise all-electronic alternative for measurement and control of molecules in living cells.
Highlights
Negative-feedback loops are important for regulation and homeostasis in biology[1,2,3,4,5,6,7,8,9,10] and in engineering[11] in both natural and synthetic systems
A microprocessor associated with the microfluidic system effectively determines the regulated value of LacZα in the bacterium, and the feedback dynamics can be altered by changing software parameters in the electronic control strategy
We have described a proof-of-concept ‘LOC’-based microfluidic chip & control system that can be used to precisely control molecules in E. coli via a synthetic circuit
Summary
Negative-feedback loops are important for regulation and homeostasis in biology[1,2,3,4,5,6,7,8,9,10] and in engineering[11] in both natural and synthetic systems They serve to architect precise and robust control of output variables in accord with a reference set-point determined by the user. To create an alternative for optical measurements that would be precise but that would be cheaper and more portable, we describe a genetic circuit in Escherichia coli with an inducible promoter controlled by an exogenous input (IPTG) and an associated transcription factor (LacI) that together serve to regulate the production of a β-galactosidase enzyme (Fig. 1). A microprocessor associated with the microfluidic system effectively determines the regulated value of LacZα in the bacterium, and the feedback dynamics can be altered by changing software parameters in the electronic control strategy
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